1. Field of the Invention
The present invention relates to a rocket shell which is composed of a composite material and has a much improved flight characteristic.
2. Description of the Prior Art
Materials that are used for the production of rocket shells are required to have light weight, high air tightness and sufficient strength. As materials meeting these requirements, there have heretofore been used high tensile strength steels, titanium alloys, aluminum alloys and magnesium alloys. In rocket shells made from these materials, taking into due consideration the burning pressure the metal thickness can be reduced to about 1 mm so as to lighten the weight and/or enhance the mass ratio of the rocket propellent. However, sophisticatd technology is required for production of rocket shells composed of such materials, and they are expensive and are not suitable for mass production.
As rocket shells having a light weight and which are suitable for mass production, there have been proposed rocket shells formed by rolling up in thin plate of a metal into a cylinder by using an adhesive and rocket shells formed by winding high tensile strength filaments into a cylinder by using an adhesive. However, in rocket shells of the former type, because thin metal plates having both a low density and a high tensile strength have not been obtained, in order to obtain a rocket shell having a sufficient tensile strength, the number of laminations or layers must be increased, and, as a consequence, the weight is inevitably increased. Rocket shells of the latter type are satisfactory in density and tensile strength, but they sill possess disadvantages such as insufficient air tightness. Rockets having fully satisfactory properties cannot be obtained using these two types of shells.
As a result of our research works made with a view to overcoming these defects based on rocket shells obtained by laminating a high tensile strength metal thin plate by a combustible adhesive, which are disclosed in Japanese Patent Application Laid-Open Specification No. 2200/76 and the specification of Japanese Patent Application No. 7607/75 (corresponding to U.S. Ser. No. 628,503, filed Nov. 3, 1975) now abandoned, replaced by continuation application Ser. No. 848 740, filed Nov. 4, 1977, now U.S. Pat. No. 4,119,036, we discovered that a rocket shell, formed by laminating in combination a high tensile strength metal thin plate and filaments having a high tensile strength by using an adhesive, has a low density and a high tensile strength and can improve the properties of the resulting rocket. Based on this finding, we have now completed the present invention. The rocket shell of the present invention has a strength that can sufficiently withstand the conventional combustion pressure of a rocket (20 to 100 Kg/cm.sup.2), it is excellent in air tightness, and is very light in weight.
In structures composed of composite materials, such as the rocket shell of the present invention, when a plurality of structural materials (principal strength-imparting materials) are employed, it is desired that they be quite similar to one another with respect to physical properties such as elongation and modulus of elasticity. More specifically, if there are large differences between the physical properties of these materials, when a force is applied to the structure, a stress is generated mainly on the material having the lowest elongation, and a sufficient strength cannot be manifested by the structure of composite materials taken as a whole. Accordingly, the respective materials should be selected taking this into due consideration.